Spectrophotometric analysis of skin lesions

What is spectrophotometric analysis?

Spectrophotometric analysis of skin lesions refers to the use of a skin imaging device to help evaluate pigmented skin lesions (moles) and make it easier to identify and diagnose early stage malignant melanomas (skin cancers).

Spectrophotometric analysis is an advanced form of dermoscopy using a computer software program that calculates and extracts information about the cells and structures of the skin. Currently, most dermoscopic devices work by using a powerful lighting system and a high quality magnifying lens. Light penetrates the skin 20 microns deep and magnified digital photographic images are taken. Spectrophotometric analysis takes dermoscopy a step further by using a light beam that penetrates to a depth of 2mm (1000x deeper) beneath the skin surface. Light images taken with a digital camera or hand-held scanner are then fed into a computer.

The SIAscope is a type of spectrophotometer. SIAscope stands for Spectrophotometric Intracutaneous Analysis and is a trademark of Astron Clinica Limited. This article describes how it works. Melafind® is another device that uses spectrophotometric analysis and is undergoing clinical trials in the USA.

How does it work?

Spectrophotometric analysis works on the principle that light energy is absorbed and remitted by particular target cells with colour (chromophores) in the skin.

1. The device emits visible and infrared light
2. Various chromophores in the layers of skin respond to the light differently and send back remitted light
3. Melanin absorbs ultra-violet light
4. Haemoglobin (red blood cells) absorb infrared light
5. Collagen absorbs and remits light across the spectrum corresponding to the size and amount of collagen cells in the deeper layers of skin (papillary dermis).
6. Reflected light received by the spectrophotometer is analysed by a computer software program that calculates the quantity of light absorbed at various wavelengths.
7. The images created from computer analysis show the presence of melanin, blood or collagen changes in the area examined. For example, melanocytes may be shown in the deeper layers of skin, which may be an early indication of melanoma.

How is spectrophotometric analysis performed?

Spectrophotometric analysis is performed using a specialised digital camera to examine the skin.

What is spectrophotometric analysis used for?

Spectrophotometric analysis is used in a number of centres in the UK, Australia and elsewhere to aid in the early detection and diagnosis of malignant melanoma. In expert hands, it has been shown to increase diagnostic accuracy from around 70% by clinical examination alone, to 95%.

Spectrophotometric analysis has only recently been introduced to New Zealand (SIAscopy). Contact the sponsor for further information for locations where these examinations can be performed.

Please note, the information used to write this page was provided by the manufacturer of the device. The New Zealand Dermatological Society's editors consider there is insufficient data to determine the role of this device in the overall management of patients at risk of melanoma.